In recent years, there has been an increased demand for a laminated piezoelectric ceramic electronic component such as a laminated piezoelectric actuator capable of obtaining a large displacement at low voltages.
Such a type of piezoelectric ceramic electronic component is generally produced by alternately laminating a piezoelectric ceramic layer and a conductive layer that is to become an internal electrode and co-sintering the laminate.
As an internal electrode material, conventionally, an Ag—Pd alloy is widely used, but the Ag—Pd alloy is relatively expensive so that most of the material cost is occupied by the internal electrode material. Also there is a drawback that sufficient reliability will not be ensured because of occurrence of migration of Ag at the time of driving the component by a low frequency area or DC voltage.
From the view point of suppressing the occurrence of migration, it is desired to use a low-migratory material. As such a low-migratory material, Pd, Pt, Ni and the like are known, but precious metal materials such as Pd and Pt are expensive, and may result in further rising in the material cost.
For effectively suppressing the occurrence of migration at a low cost, it is therefore preferred to use Ni which is available at a relatively low price.
Since Ni is easily oxidized when it is sintered in an ambient atmosphere, it need to be sintered in a reductive atmosphere, and a piezoelectric material capable of being co-sintered in a reductive atmosphere is required.
In the case of a conventional PZT (lead zirconate titanate)-based material or a PT (lead titanate)-based material, Pb will be reduced when sintering is conducted in a reductive atmosphere, so that a desired stable piezoelectric characteristic is not obtained.
On the other hand, compositions represented by the general formula: (1−n) (K1−x−yNaxLiy)m(Nb1−zTaz)O3−nM1M2O3 (M1 represents a bivalent metal element, M2 represents a tetravalent metal element, 0.1≦x, y≦0.3, x+y<0.75, 0≦z≦0.3, 0.98≦m≦1.0, 0<n<0.1) are known as piezoelectric porcelain compositions not containing Pb (Patent document 1).
Even though it is a non-lead-based composition, the piezoelectric porcelain composition described in Patent document 1 realizes such excellent piezoelectric characteristics as a dielectric constant εr of 1000 or higher, an electromechanical coupling coefficient kp of 25% or higher, and a Curie point Tc of 200° C. or higher.
Patent document 1: Japanese Unexamined Patent Publication JP-A 11-228227